Many microorganisms have evolved associations with metazoans that range from beneficial symbiosis to pathogenic. While bacteria are well recognized to form beneficial symbiotic associations with metazoans, viruses are usually viewed as non-living, parasitic entities that interact with hosts in ways that only benefit their own transmission and persistence. Yet, many viruses are vertically transmitted, [and are maintained as persistent, nondestructive associations with a wide diversity of hosts, including invertebrates and mammals. Little is currently known about how virus- and host-derived genes interact to regulate viral replication and maintain the symbiotic association. Parasitoid wasps that carry polydnaviruses provide among the strongest examples of viruses evolving into [vertically transmitted, persistent,] beneficial symbionts. [Background studies show that polydnaviruses from braconid wasps evolved from pathogenic nudiviruses but are now beneficial symbionts that persist as integrated proviruses but which replicate at a very specific time in the wasp life cycle to produce virions. However, little is known about how polydnavirus and wasp genes interact to maintain the symbiotic association or how viral replication is regulated. To address this question, I propose to focus on the wasp Microplitis demolitor and its associated polydnavirus named M. demolitor bracovirus (MdBV). My specific aims are to: 1) characterize genes involved in replication of MdBV using massively parallel sequencing technology; 2) identify genes essential for virion formation by conducting a series of functional experiments, and; 3) characterize sequences the viral polymerase binds to assess whether it transcribes only viral or also host genes by conducting chromatin immunoprecipitation (ChIP) assays together with sequencing of captured DNAs. Expected outcomes of my studies will enhance understanding of polydnavirus replication and the roles of virus- and host genes play in this process. [Long term persistence as proviruses combined with episodic replication is a widespread phenomenon in virology of great importance to numerous diseases, yet understanding of the processes that regulate viral activation remain limited to a handful of viral taxa. Thus, more broadly, my study i fundamentally important for understanding how virus and host genomes evolve to form long-term associations, how viruses can evolve to function as symbionts, and how activation/replication of large DNA viruses is regulated at the molecular level.]